UPDATE: a thin layer of PVA glue (school glue diluted in water, maybe 50/50), and allowed to dry, makes it adhere reasonably well. For small parts, like gears maybe, it allows you to print with a reasonable degree of success.
This is a log of my adventures printing POM (also known as Acetal or Delrin) with the Ender-3. I haven’t succeeded yet but here are the things I tried, and failed, so you don’t make the same mistakes.
Product: GRILON3 Acetal «Pro-Adhesion»
It’s much more widely known as Delrin. It’s a plastic with desirable mechanical properties, one of which is its low friction coefficient. It’s often used as bushing material for rolling against steel because it «self lubricates», similar to brass. Except delrin doesn’t require lubrication because it’s slicker than brass. Some prefer it as a material as leadscrew nuts, because it actually lasts longer than brass. That said, it’s still a plastic, and it won’t withstand shearing forces as good as brass (that is, hit a brass nut axially with a hammer and it may survive, but delrin nut will break).
It’s an awful material to print. The hardest thing is to get it to stick to the bed. It just won’t stick to basically anything. It’s worse than nylon.
IT WARPS LIKE NO OTHER MATERIAL.
This filament requires a relatively hot nozzle, but nothing bowden printers can’t handle.. 230 C or more. But at more than 240C, this filament is supposed to release irritant or poisonous fumes, so I’m keeping it at 235C. The filament is extremely liquid, it oozes like crazy when left in the nozzle. If pushed too fast, it has a tendency to make a «fat noodle» instead of a nozzle-sized string. In certain conditions it also has a tendency to stay molten even after deposited on the part!
This is critical. It requres a VERY HOT BED. The requirement is usually hotter than what normal beds can provide. My ender 3 maxes out at 115C. I’ve read success with printing this material at at least 150C bed temperature, but that seems excessive and probably not really necessary (more on this later).
I don’t have one. I was told by some expert not to even try if i don’t have a build chamber capable of reaching over 100C (!!!). I don’t really think this is necessary to prevent warping, at least for short pieces, since the material starts warping at even less than 1mm of printing, when it’s still at «bed temperature».
Here’s where this gets tricky. This material won’t stick to pretty much anything, but there are a few surfaces where it does.
- Glass: It positively does NOT adhere to glass
- Aluminium: Nope.
- PVA glue/gluestick: It is recommended by the manufacturer, but I haven’t succeeded in making it stick to PVA.
- Diluted contact cement: bet you never heard of this one. This was recommended in a call by the manufacturer. Basically contact cement diluted in mineral spirits. Make sure to get a contact cement that works like this. It readily sticks to this! Even on glass and aluminium
- Manila/Kraft paper: it readily sticks to this! I think this is due to the textured nature of this paper, which gives a very large surface area for it to grab on to. Unfortunately, when it warps, it just rips a layer of paper
- MDF: Seems to be the same as paper, and has the same problem, though it’s slightly tougher
- Fabric: This is much better , it adheres to fabric. In my tests I have glued down the fabric with PVA glue to glass. But this bond isn’t very strong and it warps anyways. The other problem is that the fabric bonds permanently to the bottom layer. May be OK if using a raft, but then the piece will warp off the raft…
- Wood: May be an option but I don’t have a thin piece of wood to use on my bed.
Failures and why it failed
- Temperature at 220C: nice finish, but the layers didn’t fuse. every single layer delaminated.
- PVA or gluestick on glass: did not adhere
- Manila/kraft paper: adhered, but when it warped, it just ripped the paper.
- Fabric glued to glass: adhered too well, ripped the fabric at parts. Fabric impossible to remove off print
- MDF: readily adhered but seems to have still warped. Also, MDF warps (it flexes) when heated so the bed isn’t flat.
- Diluted contact cement on glass: worked but ended up warping
- Diluted contact cement straight on alu bed: worked better, but failed. The next paragraph will go into detail
The best print so far has been with diluted contact cement and alu bed. The glass seems to lose several degrees of temperature. Removing it and printing straight on the aluminium plate gives a much higher temperature.
To make it stick, I use diluted contact cement. There’s not much to it: squeeze a teaspoon or so of contact cement on the bed, and take a small (2x2x2cm or so?) sponge full of mineral spirits. squeeze it over the cement, mix it, suck it up, squeeze it, etc. Then spread it with the sponge. Do all of this on the COLD bed. When you spred it, it will level very nicely. On glass it doesn’t even look like it’s there. Heat the bed to as hot as you can get it.
Use a very large brim, really, a ridiculously large brim. 30mm or more.
Why it failed:
I forgot to set the z-offset of my printer lower than usual (you need the nozzle to be really close to the bed). So I was trying to level it as it printed the brim. The brim ended up breaking in some parts and this is where the print failed: the pulling forces were too high and the smaller area brim failed to prevent warping. Where the brim was intact, the part did not warp
I’m now reprinting again with a bigger brim and will post updates.